I have the same issue, you can buy a replacement unit for £20 on eBay or Amazon as said above.
You can strip down the door from inside the car if you remove the rear seats, you will break the door clips, but the are very cheap to replace.
Remove all the door carrier parts, it's worth noting the door lock and window motor/regulator are connected so if you unplug the window motor the door lock won't work..
With everything removed, you will be able to reach the lock and work the leaver through it's motion, hopefully opening the door.
If not then you may need a big hammer and something long and poky to then smash it to bit until it releases the door, where you can then unbolt the rest of it and fit a replacement.... sounds harsh but it's a known method.
I would advise buying a replacement unit before smashing the other one though!